Parts

729 Articles

Flyback Converter Revealed

August 13, 2025 by 7 Comments

As [Sam Ben-Yaakov] points out in a recent video, you don’t often see flyback converters these days. That’s because there are smarter ways to get the same effect, which is to convert between two voltages. If you work on old gear, you’ll see plenty of these, and going through the analysis is educational, even if you’ll never actually work with the circuit. That’s what the video below shows: [Sam’s] analysis of why this circuit works.

The circuit in question uses a bridge rectifier to get a high-voltage DC voltage directly from the wall. Of course,  you could just use a transformer to convert the AC to a lower AC voltage first, but then you probably need a regulator afterwards to get a stable voltage.

Continue reading “Flyback Converter Revealed” →

Continuous-Path 3D Printed Case Is Clearly Superior

August 12, 2025 by 9 Comments

[porchlogic] had a problem. The desire was to print a crystal-like case for an ESP32 project, reminiscent of so many glorious game consoles and other transparent hardware of the 1990s. However, with 3D printing the only realistic option on offer, it seemed difficult to achieve a nice visual result. The solution? Custom G-code to produce as nice a print as possible, by having the hot end trace a single continuous path.

The first job was to pick a filament. Transparent PLA didn’t look great, and was easily dented—something [porchlogic] didn’t like given the device was intended to be pocketable. PETG promised better results, but stringing was common and tended to reduce the visual appeal. The solution to avoid stringing would be to stop the hot end lifting away from the print and moving to different areas of the part. Thus, [porchlogic] had to find a way to make the hot end move in a single continuous path—something that isn’t exactly a regular feature of common 3D printing slicer utilities.

The enclosure itself was designed from the ground up to enable this method of printing. Rhino and Grasshopper were used to create the enclosure and generate the custom G-code for an all-continuous print. Or, almost—there is a single hop across the USB port opening, which creates a small blob of plastic that is easy to remove once the print is done, along with strings coming off the start and end points of the print.

Designing an enclosure in this way isn’t easy, per se, but it did net [porchLogic] the results desired. We’ve seen some other neat hacks in this vein before, too, like using innovative non-planar infill techniques to improve the strength of prints.

Continue reading “Continuous-Path 3D Printed Case Is Clearly Superior” →

A pink sine wave is seen against the black background of an oscilloscope display.

Coping With Disappearing Capacitance In A Buck Converter

August 10, 2025 by 25 Comments

Designing a circuit is a lot easier on paper, where components have well-defined values, or lacking that, at least well-defined tolerances. Unfortunately, even keeping percentage tolerances in mind isn’t always enough to make sure that circuits work correctly in the real world, as [Tahmid] demonstrates by diagnosing a buck converter with an oddly strong voltage ripple in the output.

Some voltage ripple is an inherent feature of the buck converter design, but it’s inversely proportional to output capacitance, so most designs include a few smoothing capacitors on the output side. However, at 10 V and a 50% duty cycle, [Tahmit]’s converter had a ripple of 0.75 V, significantly above the predicted variation of 0.45 V. The discrepancy was even greater at 20 V.

The culprit was the effect of higher voltages on the ceramic smoothing capacitors: as the voltage increases, the dielectric barrier in the capacitors becomes less permittive, reducing their capacitance. Fortunately, unlike in the case of electrolytic capacitors, the degradation of ceramic capacitors performance with increasing voltage is usually described in specification sheets, and doesn’t have to be manually measured. After finding the reduced capacitance of his capacitors at 10 V, [Tahmid] calculated a new voltage ripple that was only 14.5% off from the true value.

Anyone who’s had much experience with electronics will have already learned that passive components – particularly capacitors – aren’t as simple as the diagrams make them seem. On the bright side, they are constantly improving.

Is It Time To Retire The TP4056?

August 8, 2025 by 30 Comments

The TP4056 is the default charge-controller chip for any maker or hacker working with lithium batteries. And why not? You can get perfectly-functional knockoffs on handy breakout boards from the usual online sources for pennies. Betteridge’s Law aside, [Lefty Maker] thinks that it may well be time to move on from the TP4056 and spends his latest video telling us why, along with promoting an alternative.

His part of choice is another TI chip, the BQ25185. [Lefty] put together his own charge controller board to show off the capabilities of this chip — including variable under- and over-charge protection voltages. Much of his beef with the TP4056 has less to do with that chip than with the cheap charge modules it comes on: when he crows about the lack of mounting holes and proper USB-PD on the knock-off modules, it occurs to us he could have had those features on his board even if he’d used a TP4056.

On the other hand, the flexibility offered by the BQ25185 is great to future-proof projects in case the dominant battery chemistry changes, or you just change your mind about what sort of battery you want to use. Sure, you’d need to swap a few resistors to set new trigger voltages and charging current, but that beats starting from scratch.

[Lefty Maker] also points out some of the advantages to making your own boards rather than relying on cheap modules. Namely, you can make them however you want. From a longer USB port to indicator LEDs and a built-in battery compartment, this charging board is exactly what [Lefty Maker] wants. Given how cheap custom PCBs are these days, it’s not hard to justify rolling your own.

The same cannot be said of genuine TI silicon, however. While the BQ25185 has a few good features that [Lefty Maker] points out in the video, we’re not sure the added price is worth it. Sure, it’s only a couple bucks, but that’s more than a 300% increase!

We’ve seen other projects pushing alternative charge controllers, but for now the TP4056 reigns as the easy option.

Continue reading “Is It Time To Retire The TP4056?” →

USB-C-ing All The Things

July 22, 2025 by 53 Comments

Wall warts. Plug mounted power supplies that turn mains voltage into low voltage DC on a barrel jack to power a piece of equipment. We’ve all got a load of them for our various devices, most of us to the extent that it becomes annoying. [Mikeselectricstuff] has the solution, in the shape of a USB-C PD power supply designed to replace a barrel jack socket on a PCB.

The video below provides a comprehensive introduction to the topic before diving into the design. The chip in question is the CH224K, and he goes into detail on ordering the boards for yourself. As the design files are freely available, we wouldn’t be surprised if they start turning up from the usual suppliers before too long.

We like this project and we can see that it would be useful, after all it’s easy to end up in wall wart hell. We’ve remarked before that USB-C PD is a new technology done right, and this is the perfect demonstration of its potential.

Continue reading “USB-C-ing All The Things” →

The 555 Writ Large

July 12, 2025 by 25 Comments

Few electronic ICs can claim to be as famous as the 555 timer. Maybe part of the reason is that the IC doesn’t have a specific function. It has a lot of building blocks that you can use to create timers and many other kinds of circuits. Now [Stoppi] has decided to make a 555 out of discrete components. The resulting IC, as you can see in the video below, won’t win any prizes for diminutive size. But it is fun to see all the circuitry laid bare at the macro level.

The reality is that the chip doesn’t have much inside. There’s a transistor to discharge the external capacitor, a current source, two comparators, and an RS flip flop. All the hundreds of circuits you can build with those rely on how they are wired together along with a few external components.

Even on [stoppi]’s page, you can find how to wire the device to be monostable, stable, or generate tones. You can also find circuits to do several time delays. A versatile chip now blown up as big as you are likely to ever need it.

Practical? Probably not, unless you need a 555 with some kind of custom modification. But for understanding the 555, there’s not much like it.

We’ve seen macro 555s before. It is amazing how many things you can do with a 555. Seriously.

Continue reading “The 555 Writ Large” →

Voltage Divider? Filter? It’s Both!

July 10, 2025 by 3 Comments

When we do textbook analysis, we tend to ignore the real-world concerns for the sake of learning. So, a typical theoretical voltage divider is simply two resistors. But if you examine a low-pass RC filter, you’ll see a single resistor and a capacitor. What if you combine them? That’s what [Old Hack EE] did in a recent video, and you can check it out below.

It helps if you are familiar with Thevenin equivalents and, of course, Ohm’s Law. There’s also a bit of algebra, but nothing too complicated. The example design has a lossy filter at 100 Hz.

Of course, RC filters are easy to understand if you think of them as voltage dividers with a frequency-variable resistance, which is what the math is basically saying. The load impedance, in this case, is R2 in parallel with Xc at a given frequency.

He mentions that you might find a circuit like this in a power supply. However, it is also common to see this circuit wherever a divider drives a load with capacitance or even parasitic capacitance in cables or circuit boards.

We’ve discussed Thevenin equivalence modeling before. If you want really good filters, you are probably going to need op-amps.

Continue reading “Voltage Divider? Filter? It’s Both!” →